Stanford University is the assignee of U.S. Pat. Nos. 5,683,438; 6,602,277; 6,673,099; 6,656,208; 6,966,922; 7,122,047; and 6,974,442. Every device disclosed in those patents is a negative pressure, thermal energy device and has the following elements: (1) an enclosure having an opening to receive a portion of a patient's body that contains a venous plexus area, (2) a vacuum system that creates a negative pressure in the enclosure, (3) a seal positioned at the enclosure's opening to maintain the negative pressure in the enclosure, and (4) a thermal energy system having a thermal energy contacting element wherein the venous plexus area is supposed to contact the thermal energy contacting element. In addition, these devices are non-disposable products.
Stanford University's Products
A. Enclosure
The enclosure surrounds a portion of a patient's body having a venous plexus area. The venous plexus area is a vascular network formed by numerous anastomoses between veins. A venous plexus area is normally located at the patient's foot area and/or hand area.
The enclosure can be shaped like a glove, a mitten, a boot, a clam-shell, or equivalents thereof so long as there is an opening that can receive the patient's body part having a venous plexus area. The enclosure is also a polymeric material that can withstand the formation of predetermined negative pressure values within its interior; the interior receives the patient's body part having a venous plexus area.
B. Seal
The seal is mounted at the enclosure's opening. The opening also receives the patient's body part having a venous plexus area. The seal establishes (1) a vacuum-tight fit between the body portion and the enclosure or (2) a soft seal fit between the body portion and the enclosure.
The term “vacuum-tight”, as interpreted by Dr. Grahn in some of the above-identified Stanford patents and he is one of the inventors of all of the Stanford patents, means a hard seal that does not leak. Dr. Grahn's interpretation conforms with General Electric's January 1966 definition of “a vacuum-tight seal is generally considered to be one which, when tested on a helium-peaked mass spectrometer leak detector, shows a leakage rate of less than 10−10 cm3s−1.”
The soft seal allows the negative pressure to leak to the ambient environment through the seal so the seal does not create a tourniquet effect on the mammal. A tourniquet effect is obtained through a hard seal and is undesirable because it terminates the blood flow which is contrary to the intent of Stanford's negative pressure, thermal energy device. Even though the soft seal leaks, the negative pressure in the enclosure is maintained by the vacuum system and the soft seal inhibits an immediate loss of the desired negative pressure in the enclosure.
C. Vacuum System
The vacuum system connects to the enclosure for establishing and, in some embodiments, maintaining a predetermined negative pressure inside the enclosure to cause vasodilation in the body portion surrounded in the enclosure. Negative pressure conditions are a pressure lower than ambient pressure under the particular conditions in which the method is performed. The magnitude of the decrease in pressure from the ambient pressure under the negative pressure conditions is generally at least about 20 mmHg, usually at least about 30 mmHg and more usually at least about 35 mmHg. The magnitude of the decrease may be as great as 85 mmHg or greater, but typically does not exceed about 60 mmHg and usually does not exceed about 50 mmHg. Applying the negative pressure condition to a portion of the body in the enclosure (a) lowers the vasoconstriction temperature and/or (b) increases vasodilation in the body portion that is in the enclosure.
The negative pressure inducing element may be actuated in a number of different ways, including through motor driven aspiration, through a system of valves and pumps which are moved through movement of the mammal in a manner sufficient to create negative pressure in the sealed environment.
D. Thermal Energy Contacting Element
The thermal energy contacting element delivers heated thermal energy and/or cold thermal energy at least to the surface of the body portion in the enclosure. While delivering the desired thermal energy, the vacuum system maintains the predetermined negative pressure in the enclosure. That way the local vasodilation in the body portion promotes absorption and transfer of the thermal energy from the surface of the body portion to the body core of said mammal.
The thermal energy contacting element has been disclosed as (a) “a radiant heat lamp” positioned exterior to the enclosure and provides radiant heat to the exterior surface of the enclosure which warms the interior of the enclosure and thereby provides warm thermal energy to the entire body portion in the enclosure—not just a specific portion of the body portion in the enclosure, and (b) warming or cooling blankets, warm or cool water immersion elements, warming or cooling gas elements, and a curved metal plate or a metal tube positioned in the interior of the enclosure. The latter embodiments can have a fluid (i) circulate within and (ii) not contact the body portion in the desired area—the venous plexus area.
Of these embodiments, the metal plate and tube are considered to be the most effective thermal energy contacting elements because they are easy to manufacture, the thermal energy transfer efficiency to the patient are relatively acceptable and the ease of using the product in actual use.
The fluid temperature can be thermally controlled and delivered to the thermal energy contacting element by Gaymar's Medi-Therm III fluid thermal control dispensing unit.
Grahn et al. does not disclose using positive pressure or equivalent thereof to obtain the desired therapy. As a matter of fact, Grahn et al. teaches away from using positive pressure because positive pressure will not create the desired vasodilation.
It has been determined that continuous and/or extended periods of application of negative pressure on a patient may cause edema. Edema should be avoided when possible.
Reversing Edema
In U.S. Pat. No. 6,488,643, Tumey, et al. wrote, “Among the predominant theories for explaining the effects of compression bandaging, edema reduction and control for the improvement of venous hemodynamic abnormality concomitant prolonged venous hypertension from valvular incompetency or dysfunction stands out. It is thought that the reduction and control of edema improves capillary microcirculation, in turn resulting in the elimination of venous ulcers . . . . [I]t is important to note that it is universally understood that a proper gradient must be established in order to derive the benefits of compression bandaging. This gradient is generally accepted as being from about 35 to 45 mm Hg at the ankle and reducing to about 15 to 20 mm Hg at just below the knee. Often stated in the literature as a prerequisite to good bandaging technique, the maintenance of graduated compression is critical to effective treatment of ulcers. Failure to initially obtain, and thereafter maintain, the desired sub-bandage pressures is fatal to the treatment regimen . . . . Studies show that mechanically produced compression levels may produce ischaemic not noted at similar compression levels obtained through bandaging. The reductions in leg pulsatile blood flow associated with mechanical prophylaxes often occur at compression levels below that necessary for good bandaging effects. This result, sometimes called cuffing, has resulted in most mechanical prevention prophylaxes being contraindicated for patients exhibiting DVT. Consequently, those of ordinary skill in the art have to date steadfastly avoided mechanical prophylaxes for the treatment of venous stasis and other ulcers or edema of the extremities.”
Tumey, et al. clearly teaches using any air pressure device to reverse edema is contraindicated.